Generalized valence bond molecular dynamics at constant temperature

The Nose! ± Hoover chain thermostat of Martyna, Klein and Tuckerman has been adapted to work with our generalized valence bond ab initio molecular dynamics (AIMD) method, allowing us to perform AIMD in the canonical ensemble (constant number of particles, temperature, and volume). The canonical ensemble is ideal for simulated annealing, which can be used to ® nd global potential energy minima. The e cacy of constant-temperature-based AIMD simulated annealing is demonstrated for a Si ’ cluster and is compared with that of a non-constant-temperature-based method. It is found that in comparison with the velocity-scaling approach to annealing, constanttemperature-based annealing gives better control over the annealing process and, at least in the case under study, results in attainment of the preferred geometry of the system more e ciently.